The present invention relates to a process for wastewater filtration. More particularly, the invention provides a multi-stage press apparatus for automatic sludge dewatering.
Many innovative sludge dewatering technologies and products have been implemented in order to address issues related to better performance, higher throughput or cost efficiency. Due to concerns about global warming and energy costs, there has been an effort to employ systems which consume less electrical power, chemicals and washing water.
Any wastewater and sludge process requires dewatering in order to minimize transportation and disposal volumes. Usually sludge is transported after the clarification, inefficiently, due to having a high, 89-90% liquid content.
As an example, with a daily wastewater volume of 100 cubic meters per day at solids concentration of 1000 parts per million, and when the clarifier used is DAF (dissolved air filtration), then an approximate sludge yield is approximately 2000 kg, or approximately 2 cubic meters per day, which contains approximately 5% dry solids. After pressing, the volume of this sludge that contains 30% Dry solids reaches approximately 330 liters (disposal volume).
The three major methods of achieving this dryness are plate filter press, belt press, and centrifugal decanter.
Belt press and centrifugal decanters have proven to be too large and uneconomical for the volume in the example above, besides having other drawbacks, such as high power consumption and being too mechanically complex and therefore costly.
Filter presses are usually manually operated and, therefore, require close operator attention. These presses quickly become dirty, necessitating periodical filter media cleaning.
In U.S. Pat. No. 5,614,092 to Di Leo, there is disclosed a filter system for the separation of solids and liquids from industrial muds. The filter in the system includes a deformable membrane and a fluid pump which varies the size of the volume of the membrane, thereby squeezing the filter.
While alleviating many of the tasks related to dewatering muds, such as squeezing and filtering, the filter disclosed in this patent does not address the need to minimize the down time due to the need to remove and clean the filter between the filtering operations, and, furthermore, does nothing to eliminate the need for man-hour input required for the cleaning.